Water in coesite: Incorporation mechanism and operation condition,solubility and P-T dependence, and contribution to water transport and coesite preservation
文献类型：CNKI期刊论文
| 作者 | Wei Yan; Yanyao Zhang; Yunlu Ma; Mingyue He; Lifei Zhang; Weidong Sun ; Christina Yan Wang; Xi Liu
|
| 发表日期 | 2021-01-12 |
| 出处 | Geoscience Frontiers
 |
| 关键词 | Coesite preservation FTIR New IR experimental Protocol Anhydrous minerals P-T dependence of water solubility Water-incorporation mechanism |
| 英文摘要 | A series of coesite,coexisting with or without a liquid phase,was synthesized in the nominal system SiO_2-H_2 O at800-1450℃ and 5 GPa.Micro-Raman spectroscopy was used to identity the crystalline phase,electron microprobe and LA-ICP-MS were employed to quantity some major and trace elements,and unpolarized FTIR spectroscopy was applied to probe the different types of hydrogen defects,explore water-incorporation mechanisms and quantify water contents.Trace amounts of A1 and B were detected in the coesite.Combining our results with the results in the literatures,we have found no positive correlation between the Al contents and the "Al"-based hydrogen concentrations,suggesting that previously proposed hydrogen-incorporation mechanism H~++Al~(3+)■Si~(4+) does not function in coesite.In contrast,we have confirmed the positive correlation between the B contents and the B-based hydrogen concentrations.The hydrogen-incorporation mechanism H~++B3~+■Si~(4+) readily takes place in coesite at different P-T conditions,and significantly increases the water content at both liquid-saturated and liquid-undersaturated conditions.For the SiO_2-H_2 O system,we have found that type-Ⅰ hydrogarnet substitution plays a dictating role in incorporating water into coesite at liquid-saturated condition,type-II hydrogarnet substitution contributes significantly at nearly dry condition,and both operate at conditions in between.The water solubility of coesite,as dictated by the type-Ⅰ hydrogarnet substitution,positively correlates with both P and T,c_(H_2 O)=-105(30)+5.2(32)×P+0.112(26)×T,with c_(H_2 O) in wt ppm,P in GPa and T in ℃.Due to its low water solubility and small fraction in subducted slabs,coesite may contribute insignificantly to the vertical water transport in subduction zones.Furthermore,the water solubility of any coesite in exhuming ultra-high pressure metamorphic rocks should be virtually zero as coesite becomes metastable.With an adequately fast waterdiffusion rate,this metastable coesite should be completely dry,which may have been the key factor to the partial preservation of most natural Coe.As a byproduct,a new IR experimental protocol for accurate water determination in optically anisotropic nominally anhydrous minerals has been found.Aided with the empirical method of Paterson(1982) it employs multiple unpolarized IR spectra,collected from randomly-orientated mineral grains,to approximate both total integrated absorbance and total integrated molar absorption coefficient.Its success relies on a high-level orientation randomness in the IR analyses. |
| 文献子类 | CNKI期刊论文 |
| 资助机构 | financially supported by the DREAM project of MOST, China (Grant No. 2016YFC0600408) ; the Strategic Priority Research Program (B) of Chinese Academy of Sciences (Grant No. XDB18000000) ; the Program of the National Mineral Rock and Fossil Specimens Resource Center from MOST, China |
| 卷 | v.12期:01页:319-332 |
| 语种 | 英文; |
| 分类号 | P574 |
| ISSN号 | 1674-9871 |
| 源URL | [http://ir.qdio.ac.cn/handle/337002/187903]  |
| 专题 | 中国科学院海洋研究所 |
| 作者单位 | 1.SchoolofEarthandSpaceSciences,PekingUniversity 2.KeyLaboratoryofOrogenicBeltsandCrustalEvolution,MinistryofEducationofChina 3.DepartmentofGeologicalSciences,JacksonSchoolofGeosciences,TheUniversityofTexasatAustin 4.SchoolofGemmology,ChinaUniversityofGeosciences(Beijing) 5.CenterofDeepSeaResearch,InstituteofOceanography,ChineseAcademyofSciences 6.KeyLaboratoryofMineralogyandMetallogeny,GuangzhouInstituteofGeochemistry,ChineseAcademyofSciences |
| 推荐引用方式 GB/T 7714 | Wei Yan,Yanyao Zhang,Yunlu Ma,et al. Water in coesite: Incorporation mechanism and operation condition,solubility and P-T dependence, and contribution to water transport and coesite preservation. 2021. |
入库方式： OAI收割
来源：海洋研究所
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